At the heart of global oil demand in China, there remains darkness. Oil’s collapse in 2014 has been a tale of gushing supply, but it is worth remembering that investors started the year feeling jittery about slowing demand. That centered around China, the world’s largest contributor to oil demand growth in recent years. The problem for investors next year isn’t only that Chinese demand still looks slow . It is also inscrutable. Most observers can’t agree on how much oil China actually burns. A few days before 2014 ends, the International Energy Agency says China will consume 2.5% more barrels this year than in 2013. Wood Mackenzie reckons 3.4%. IHS Energy Insight thinks 2% and Barclays 1.1%. Why the differences? Analysts infer demand by combing through refinery output, trade and inventory of products such as gasoline. This being China, questions surround most data, especially inventories, with guesswork often needed. […]